Add support for dial tones

Signed-off-by: Knut Ahlers <knut@ahlers.me>

src/app.vue

@@ -61,7 +61,7 @@ export default {
 
   computed: {
     keys() {
-      return [1, 2, 3, 4, 5, 6, 7, 8, 9, '+', 0]
+      return [1, 2, 3, 4, 5, 6, 7, 8, 9, '*', 0, '#']
     },
   },
 
@@ -95,6 +95,11 @@ export default {
     },
 
     keyDown(key) {
+      if (this.ongoingCall) {
+        this.phone.conn.sendDigits(key)
+        return
+      }
+
       this.number = `${this.number}${key}`
     },